"The cause of the absence of trees on the upland prairies is the problem most important to the agricultural interests of our state, and it is the inquiry which alone I propose to consider, but cannot resist the remark that wherever we do find timber throughout the broad field of prairie, it is always in or near the humid portions of it, as along the margins of streams, or upon or near the springy uplands. Many most luxurious growths are found in the highest portions of the uplands, but always in the neighborhood of water. For a remarkable example, I may refer to the great chain of groves extending from and including the Au Sable grove on the east and Holderman's grove on the west, in Kendall county, occupying the high divide between the waters of the Illinois and the Fox rivers. In and around all the groves flowing springs abound, and some of them are separated by marshes, to the borders of which the great trees approach, as if the forests were ready to seize upon each yard of ground as soon as it is elevated above the swamps. Indeed, all our groves seem to be located where the water is so disposed as to protect them, to a greater or less extent, from the prairie fire, although not so situated as to irrigate them. If the head waters of the streams on the prairies are most frequently without timber, as soon as they have attained sufficient volume to impede the progress of fires, with very few exceptions, we find forests on their borders, becoming broader and more vigorous as the magnitude of the streams increase. It is manifest that the lands located on the borders of streams which the fire cannot pass, are only exposed to one-half the fires to which they would be exposed, but for such protection. This tends to show, at least, that if but one-half the fires that have occurred had been kindled, the arboraceous growth could have withstood their destructive influences, and the whole surface of what is now prairie would be forest. Another confirmatory fact, patent to all observers, is, that the prevailing winds upon the prairies, especially in the autumn, are from the west, and these give direction to the fires. Consequently, the lands on the westerly sides of the streams are the most exposed to the fires, and, as might be expected, we find much the most timber on the easterly sides of the streams." [Illustration: A Section of the Grand Prairie in Benton County, Indiana, which extends west to Peoria, Illinois.]